1bli
From Proteopedia
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BACILLUS LICHENIFORMIS ALPHA-AMYLASE
Overview
BACKGROUND: The structural basis as to how metals regulate the functional, state of a protein by altering or stabilizing its conformation has been, characterized in relatively few cases because the metal-free form of the, protein is often partially disordered and unsuitable for crystallographic, analysis. This is not the case, however, for Bacillus licheniformis, alpha-amylase (BLA) for which the structure of the metal-free form is, available. BLA is a hyperthermostable enzyme which is widely used in, biotechnology, for example in the breakdown of starch or as a component of, detergents. The determination of the structure of BLA in the, metal-containing form, together with comparisons to the apo enzyme, will, help us to understand the way in which metal ions can regulate enzyme, activity. RESULTS: We report here the crystal structure of native, metal-containing BLA. The structure shows that the calcium-binding site, which is conserved in all alpha-amylases forms part of an unprecedented, linear triadic metal array, with two calcium ions flanking a central, sodium ion. A region around the metal triad comprising 21 residues, exhibits a conformational change involving a helix unwinding and a, disorder-->order transition compared to the structure of metal-free BLA., Another calcium ion, not previously observed in alpha-amylases, is located, at the interface between domains A and C. CONCLUSIONS: We present a, structural description of a major conformational rearrangement mediated by, metal ions. The metal induced disorder-->order transition observed in BLA, leads to the formation of the extended substrate-binding site and explains, on a structural level the calcium dependency of alpha-amylases. Sequence, comparisons indicate that the unique Ca-Na-Ca metal triad and the, additional calcium ion located between domains A and C might be found, exclusively in bacterial alpha-amylases which show increased, thermostability. The information presented here may help in the rational, design of mutants with enhanced performance in biotechnological, applications.
About this Structure
1BLI is a Single protein structure of sequence from Bacillus licheniformis with CA and NA as ligands. Active as Alpha-amylase, with EC number 3.2.1.1 Structure known Active Sites: CA1, CA2, CA3, CS and NA1. Full crystallographic information is available from OCA.
Reference
Activation of Bacillus licheniformis alpha-amylase through a disorder-->order transition of the substrate-binding site mediated by a calcium-sodium-calcium metal triad., Machius M, Declerck N, Huber R, Wiegand G, Structure. 1998 Mar 15;6(3):281-92. PMID:9551551
Page seeded by OCA on Mon Nov 5 15:55:35 2007
